David A. Houlden

Early somatosensory evoked potential grades in comatose traumatic brain injury patients predict cognitive and functional outcome.

Objectives:To relate early somatosensory evoked potential grades from comatose traumatic brain injury patients to neuropsychological and functional outcome 1 yr later; to determine the day (within the first week after traumatic brain injury) that somatosensory evoked potential grade best correlates with outcome; to determine whether somatosensory evoked potential grade improvement in the first week after traumatic brain injury is associated with improved outcome. Design:Prospective cohort study. Setting:Critical care unit at a university hospital. Patients:Median nerve somatosensory evoked potentials were obtained from 81 comatose patients with traumatic brain injury. Somatosensory evoked potential grades were calculated from results obtained on days 1, 3, and 7 after traumatic brain injury. Glasgow Outcome Scale, Barthel Index, Rivermead Head Injury Follow-up Questionnaire, General Health Questionnaire, Stroop Color-Word Test, Paced Auditory Serial Addition Task, and Symbol-Digit Modalities Test scores were obtained 1 yr after injury. Interventions:None. Measurements and Main Results:Somatosensory evoked potential grade on days 1, 3, and 7 related significantly with Glasgow Outcome Scale and Barthel scores (day 3 better than day 1) but did not relate with Rivermead Head Injury Follow-up Questionnaire or General Health Questionnaire scores. Day 3 and day 7 somatosensory evoked potential grades related significantly with Stroop scores. Day 3 somatosensory evoked potential grades related significantly with Symbol-Digit Modalities Test scores. Patients with bilaterally present but abnormal somatosensory evoked potentials, whose somatosensory evoked potential grade improved between days 1 and 3, had marginally better functional outcome than those without somatosensory evoked potential grade improvement. Conclusions:Day 3 somatosensory evoked potential grade related to information-processing speed, working memory, and the ability to attend to tasks 1 yr after traumatic brain injury. Day 3 somatosensory evoked potential grade had the strongest relationship with functional outcome. Somatosensory evoked potential grades were not related to emotional well-being.

A novel method in predicting immediate postoperative facial nerve function post acoustic neuroma excision.

Abstract: To determine whether the percentage calculated by dividing the amplitude of postexcision direct facial nerve stimulus responses (at pontomedullary junction) by the amplitude of distal ipsilateral transcutaneous (stylomastoid region) maximal stimulus responses and response amplitude progression by increasing stimulus intensities have predictive value for determining normal or near-normal (House-Brackmann Grade 1 or 2) immediate postoperative facial nerve function. Study Design: Intraoperative recordings of three muscle groups: 1) frontalis, 2) orbicularis oculi, and 3) orbicularis oris. Postexcision direct facial nerve stimulation at the pontomedullary junction and transcutaneous maximal facial nerve stimulation at the ipsilateral stylomastoid region and their associated response amplitudes were recorded. Setting: Tertiary referral center. Patients and Methods: Patients who underwent acoustic neuroma surgery from January 2004 to March 2006 with intraoperative facial nerve monitoring and an intact facial nerve after tumor excision were included. Recordings were available for 38 patients. Results: With a stimulus intensity of 0.3 mA at the root exit zone, there was an 81% positive predictive value in patients that exhibited a compound action potential of greater than 20% of maximum (sensitivity, 81%). This increased to 93% when the compound action potential was greater than 50% of maximum. When the amplitude increase was greater than 5 &mgr;V, there was a 77% positive predictive value (sensitivity, 87%). Conclusion: The percentage of the response amplitude of direct facial nerve stimulation at the pontomedullary junction when compared with the maximum response amplitude of ipsilateral transcutaneous stimulation at the stylomastoid foramen is a good predictor of normal to near-normal immediate postoperative facial nerve function. Progression of amplitude response also seems to be a good predictor of normal to near-normal immediate postoperative facial nerve function.

Facial nerve prognostication in vestibular schwannoma surgery: The concept of percent maximum and its predictability

To evaluate percent maximum as an intraoperative facial nerve measurement for the long‐term prognostication of vestibular schwannoma surgery.

Optimal intraoperative somatosensory evoked potential stimulus intensity can be determined by nerve action potential amplitude.

Purpose: Muscle twitch threshold has been used to determine optimal stimulus intensity for somatosensory evoked potentials but neuromuscular blockade precludes the use of muscle twitch during surgery. Accordingly, nerve action potential (NAP) amplitude was investigated as a surrogate to muscle twitch. Methods: The ulnar and tibial nerves were stimulated at the wrist and ankle, respectively, in 27 patients undergoing spine and brain surgery. After neuromuscular blockade was gone, the stimulus intensity for just maximal NAP amplitude recorded from Erbs point and the popliteal fossa was compared with the stimulus intensity for hypothenar and plantar foot muscle twitch threshold (times two), respectively (Wilcoxon matched pairs test). Results: There was no significant difference between stimulus intensity for just maximal Erb’s point and popliteal fossa NAP amplitude when compared with stimulus intensity for hypothenar and plantar foot twitch threshold (times two), respectively. Eight patients required more than twitch intensity (times two) to obtain maximum NAP. Conclusions: The NAP amplitude may be used to determine optimal somatosensory evoked potential stimulus intensity when muscle twitch is not visible. This method should improve the success of intraoperative somatosensory evoked potential monitoring and decrease erroneous interpretation.

15.Intraoperative neurophysiological spinal cord monitoring

Benign epilepsies of infancy are entities for which is not easy to make a diagnosis. In 1963 Fukuyama first proposed the benign epilesy of infancy characterized by onset before the age of 2 years and benign course. Later publications in 80s and 90s specified localization and semiology, familial and nonfamilial characteristics and final outcome. The International classification of epilepsies and epileptic syndromes (Engel, 2001) comprises only familial and non-familial benign infantile seizures. Specchio and Vigevano (2006) described semiology and onset, family history, ictal and interictal EEG pattern, prognosis and final outcome of benign seizures in infancy. They divided them into the following groups: Benign non-familial infantile seizures, Benign familial infantile seizures (BFIS), BFIS associated with other neurological symptoms, Benign familial neonatalinfantile seizures (BFNIS), Benign infantile seizures associated with mild gastroenteritis (BIS with MG), Benign infantile focal epilepsy with midline spikes and waves during sleep (BIMSE). The aim of this review is to describe these entities and discuss similarities and difference between them. We pointed out significance of video EEG recording in dramatic appearance of seizures in clusters, lasting few days, which can also occured in benign epilepsy of infancy.

A novel method for making dorsal horn lesions

Objective. Dorsal root entry zone (DREZ) lesioning for intractable pain currently requires a multi-level laminectomy for direct access to all spinal cord segments intended to be lesioned. The hypothesis is that a silastic rubber catheter can be inserted into the dorsal horn (through a single laminectomy site) and advanced down several spinal cord segments, while staying exclusively in the dorsal horn. Methods. A cervical laminectomy was performed in four sheep. Standard cerebrospinal fluid drainage catheters were introduced into the dorsal horn through a small incision in the DREZ. The catheters were advanced caudally along the longitudinal cord axis for a distance of 8–11 cm. Neurophysiological monitoring was done. The cord was excised from the spinal canal, fixed in formalin and cut in serial axial slices at 1 cm intervals to assess the position of the catheter within the spinal cord. Results. The catheter stayed within the grey column of the spinal cord dorsal horn, along the entire length of its insertion. Electrophysiological data confirmed that dorsal horn activity was totally ablated after catheter passage in three sheep, and partially ablated in the fourth. Conclusion. The intrinsic architecture of the spinal cord tissue allows the predictable passage of the catheter through the column of dorsal horn grey matter. Dorsal horn lesioning can be accomplished without direct access to the cord segments selected for surgery.

Sleep apnea following oropharyngeal cancer treatment

vessel formation in many cancers, but their role in mobilization and homing to TPD remains uncharacterized. Although estrogen is believed to be a major stimulus for BM-EPC mobilization, its function as a mobilizing agent in TPD has not been explored. We propose to test whether estrogen can mobilize BM-EPCs to orthotopically implanted thyroid tumors. METHODS: Ovariectomized female BALB/c nude mice underwent bone marrow transplantation obtained from transgenic Tie2/GFP mice in which GFP is under the endothelial cell specific Tek promoter, thus facilitating EPC detection. One week prior to orthotopic KAT50-TS (human goiter cell line) cell implantation, mice were either supplemented or not supplemented with 90-day slow release estradiol pellets. Tumors were harvested and analyzed for presence of GFP positive EPCs. RESULTS: Incorporation of GFP-tagged BM-EPCs into thyroid vasculature was examined by fluorescent microscopy. Orthotopically injected KAT50-TS tumors were compared to sham injected thyroid tissue. In estradiol supplemented mice, increased numbers of GFP-tagged BM-EPCs were found to integrate into the KAT50-TS tumor neovasculature. In contrast, very few GFP-tagged BM-EPCs targeted normal thyroid tissue. CONCLUSIONS: Estradiol significantly affected tumor neovascularization via induction of BM-EPCs in an orthotopic model of thyroid cancer. Understanding the mechanisms of E2-induced mobilization of EPC from the bone marrow will open a new area of thyroid cancer research. BM-EPCS could potentially serve as the Trojan horse to deliver bio-molecules that disrupt tumor vasculogenesis and induce targeted killing of tumor cells.

A novel method for VEMP: The technique and reproducibility

METHODS: Three-dimensional (3-D) images of membranous labyrinth were reconstructed from 31 normal temporal bones, 6 temporal bones from 3 patients with bilateral Ménière’s, 16 temporal bones from 8 patients with unilateral Ménière’s. Volumes of each part of membranous labyrinth were measured in each temporal bone group after 3-D reconstruction. RESULTS: The mean volumes and normal volume-limits of the cochlear duct, saccule, and utricle were 7.67 and 9.77, 2.42 and 3.68, and 10.65 and 16.45 mm3, respectively. All 3 patients with bilateral Ménière’s disease showed endolymphatic hydrops in both sides of ear. Of 8 patients with unilateral Ménière’s disease, 5 had no symptom in the contralateral ear, whereas 3 had histories of progression from unilateral to bilateral Ménière’s disease. All diseased (8 ears) and all symptomatic contralateral sides (3 ears) showed endolymphatic hydrops. In contrast, no hydrops was observed in any part of membranous labyrinth in the contralateral ears (5 ears). CONCLUSIONS: Our findings suggest that endolymphatic hydrops contribute to the onset of symptoms in the patients with Ménière’s disease. In addition, the volume data obtained from this study could be useful for the assessment of hydrops in the diagnostic imaging of the inner ear of Ménière’s disease.

Gender as a Predictor of Hearing Preservation Outcome in Acoustic Neuroma Surgery

Introduction: The correlation between gender and likelihood of preservation of serviceable postoperative hearing in acoustic neuroma surgery has seldom been reported. The limited available data suggest that, when preoperative tumor size and hearing are comparable, males have a greater likelihood of preservation of some postoperative hearing (p < 0.05 at best). Methods: A consecutive series of 184 retrosigmoid procedures for removal of unilateral acoustic neuromas (AN), in the period ending June 30, 2005, were subjected retrospectively to linear regression analysis for factors predictive of successful postoperative preservation of Gardner and Robertson Class 1 and 2 hearing (HP). These cases were selected on the basis of size (mean extracanalicular diameter < 20 mm) and preoperative hearing, and form part of a larger series of 810 consecutive cases of unilateral AN. Variables examined included age, gender, side and size of tumor, preoperative hearing, and intraoperative cochlear nerve compound action potential (CAP) threshold shift. Results: Overall HP rate was 34.4% (53.8% for intracanalicular AN). Size (p < 0.001), intraoperative CAP threshold shift (p < 0.0001), and female gender (p = 0.01) were predictors of HP. Male-female ratio for the series was 47/53. Age (p = 0.37) and tumor size (p = 0.20) did not differ between males and females. Postoperative HP occurred in 25.4% of males and 44.2 % of females, respectively (p = 0.01). Conclusions: Though female gender has not previously been identified as a predictor of greater likelihood of preservation of serviceable postoperative hearing in AN surgery, the present study strongly suggests that this is the case. Gender difference should probably be taken into account in preoperative discussion of outcome, at least in our hands, and may have other implications as well.